Production of iron-nickel alloys from low grade ores



R. PERRIN June 12, 1956 PRODUCTION OF IRON-NICKEL ALLOYS FROM LOW GRADEORES 3 Sheets-Sheet 1 Filed June 9, 1953 INVENTpR. Rene Parr/n H/ATTORNEYS R. PERRIN June 12, 1956 PRODUCTION OF IRON-NICKEL ALLOYS FROMLOW GRADE OREIS Filed June 9, 1953 3 Sheets-Sheet 2 INVENTOI; ReneParr/n H/S ATTORNEYS R. PERRIN June 12, 1956 PRODUCTION OF IRON-NICKELALLOYS FROM LOW GRADE ORES 3 Sheets-Sheet 3 Filed June 9, 953

INVENTOR: Rene Per/m HIS TTOR/VE Y8 United States Patent PRODUCTION OFIRON-NICKEL ALLOYS FROM LOW GRADE ORES,

Rene Perrin, Paris, France, assignor to Societe dElectro- ChimiedElectro-Metallurgie et des Acieries Electriques dUgine, Paris, FranceApplication June 9, 1953, Serial No. 360,580 Claims priority,application France June 21, 1952 12 Claims. (Cl. 75--133.5)

There are in the world important deposits of such low grade nickel ores.Chemical or metallurgical methods are now known for treating themtoextract the nickel.

therefrom, but such methods are very costly. I

An object of the present invention is to provide a process and apparatusfor recovering nickel from such ores in an economical manner and in sucha way as to produce ferro-nickel of high nickel content of the order of25 to 60% nickel for instance, the nickel content usually being betweenabout 25 and 40%. Such ferro-nickel alloys may be used as substitutesfor pure nickel in almost every instance where nickel is employed insteel making processes.

The process can be carried out in a continuous or a discontinuousmanner, the former being the preferred practice.

In the accompanying drawings which illustrate several forms of apparatussuitable for carrying out the process in a continuous manner,

Figure 1 is a longitudinal section through a rotatable vessel andassociated parts;

Figure 2 is a transverse section taken on the line I I'--II of Figure l;

Figure 3 is a view similar to Figure 1, but illustrating a modified formof rotatable vessel;

Figure 4 is a transverse section taken on the line IV--IV of Figure 3; v

Figure 5 is a transverse section taken on the line V-V' of Figure 3;

Figure 6 is a view similar to Figure 1, but illustrating anotherembodiment of the rotatable vessel; and

Figure 7 is a transverse section taken on the line VII- VII of Figure 6.i

Applicants Patent 2,100,265 granted November 23, 1937, discloses adiscontinuous process for introducing nickel into a steel bath byviolently intermixing such bath with a slag containing nickel oxide. Aparticularly convenient operating method consists in violently pouringthe molten steel into a ladle containing the slag, The

reaction is practically instantaneous. Such process-is quite suitable ifonly small amounts of nickel are-to, be introduced into steel from slagscontaining relatively large proportions of nickel oxide. However, itisnot suitable for introducing large amounts of nickel into steel from lowgrade nickel ores containing small proportions of nickel oxide.

According to the example given in the patent, a charge of 15,000 kgs. ofmolten steel is poured into a ladle containing 1,750 kgs. of molten slagcontaining oxide of the alloying metal. Using these proportions butsubstituting an ore containing 10% of nickel oxide for the slag, it ispossible to introduce about 0.9% of nickel into the steel. If the orecontains 5% of nickel oxide, the amount of steel only about 0.14% ofnickel.

ice

, 2- nickel introduced into the steel is about 0.4% and if the orecontains 1.5% of nickel oxide, the amount of nickel introduced into thesteel is about 0.14%. It will be seen that according to the method ofthe patent, only a relatively small amount of nickel can be introducedinto the steel if a low grade nickel ore is employed.

An object of the present invention, on the contrary, is to start With alow grade nickel ore containing not over about 10% nickel oxide, usuallynot over about 6% of nickel oxide, and often containing only about 1.5%nickel oxide, and to extract from this ore'almost the whole nickelcontent and to recover it in the form of a high grade alloy containing asubstantial amount of nickel, usually from 25 to 40% of nickel, whichcan be used for introducing nickel in steel making or othermetallurgical processes.

As stated above, if the proportions of steel and slag the treatment of alow grade nickel ore containing.1;5 nickel oxide, the process results inintroducing into the Such alloy because ofits low nickel content isentirely unsuitable for steel making purposes, particularly for themanufacture of nickel-chromium stainless steels, which require largeamounts of nickel. On the other hand, if it is desired to produce fromthis ore a high grade nickel alloy suitable for ,steel making andcontaining, say, 25% of nickel by the single violent intermixing of themolten ore and molten steel as taught in this patent, theweight of steelused must be very small in comparison with the weight of the ore, forinstance about 50 kgs. of steel for one ton of ore, which is a ratio ofore to steel of about 20:1. (Throughout this specification, the termton" means a metric ton of 1,000 kilograms.) In such case, the volume ofthe ore compared to that of the metal is considerable and it isimpossible, even though both phases be violently intermixed, to obtainequilibrium between the metal and all parts of the ore. Consequently,the yield of nickel is very low. This treatment is therefore eco-'nomically prohibitive when using low grade ores.

I have found that a high grade molten ferro-nickel containing 25% ormore by weight of nickel, and even upwards of 40% by weight, can be usedsuccessfully for effecting substantially complete reduction of nickeloxide in a molten, low grade nickel ore in which the nickel content ismuch lower than in the ferro-nickel. I have found further that byrepeated or continuous use of a molten ferrous metal in the treatmentof'successive quantities of the molten ore, each portion of ore treatedthereby can be substantially completely denickelized, and at the sametime, the nickel content of the ferrous metal can be progressivelyincreased to a value much above that of the ore itself, and even to avalue substantially above 25 by weight.

Based on these findings, the process of the present invention forextracting nickel from low grade oxidic nickel ores comprises forming amolten bath of said ore metal, at least in the later of said repeatedintermixings,

is a ferro-nickel containing a substantially higher percentage of nickelthan is contained in the ore itself. Indeed, the ferro-nickel willeventually contain at least 25 by weight of nickel and may contain asmuch as 40% or more by weight up to a maximum of about 60% by weight.(If the nickel content of the ferro-nickel ex- W ass 7 3 ceeds about 60%by weight, the conditions of equilibrium between ore and metal becomeless and less efiective for accomplishing a substantially completedenickelizing of the low grade oxidic nickel ores.) The quantity offerrous metal or ferro-nickel used in the treatment of each quantity ofmolten nickel ore will always contain a substantially greater weight ofiron than the Weight of nickel in the me, in order to insuresubstantially complete reduction of the nickel oxide. As regards thequantity of ferrous metal to be employed for a given amount of slag, itis preferable to employ an amount of ferrous metal or ferro-nickel whichis not less than about of the weight of molten ore and mostadvantageously the ratio of the weight of the ferrous metal orferronickel to the weight of molten ore treated thereby is in the rangefrom /2 to 2. For manyores, the weight of the ore should beapproximately equal to the weight of the metal by which it is treated.

If the ore is very low in nickel oxide, it is advisable to use arelatively small amount of ore, these conditions being'necessary toproduce a complete reaction between the metal and the ore whenbothphases are thoroughly intermixed together, andthereby to insure thebest exhaustion of the o rel The degree of exhaustion of the ore is allthe more important from an economical point, the smaller the amount ofnickel oxide in the ore. For example, if 0.30% nickel oxide is retainedin the exhausted ore, this has a much greater relative importance in thefinal cost of the ferronickel obtained, if one starts with orecontaining, say, 1.2% ofnickel oxide, than if one starts with an orecontaining, say, 4% of nickel oxide; In the first case, the exhaustionwill be about 75%; in the second, about 92%. Preliminary tests will inany case help determine the optimurn amount of ore to be used with agiven weight of metal; i

Various ways in which the process can be carried out in a discontinuousmanner will now be described.

Discontinuous Processes In carrying out the process, the molten ore andmolten steel oro'theriferrous metal are violently intermixed; The ironof the bath reduces the nickel oxide of the, ore to nickel which entersthe bath. In some cases, a small amount of strong reducing agent such asterm-silicon or ferro aluminum is introduced into the metal bath priortqor during mixing. Whether or not a reducing agent is introduced intothe metal bath, the denickelized ore is separated from the metal bathafter the intermixing andthe metal bath, is repeatedly intermixed withsuccessive further charges ofmolten low grade nickel ore under. theconditions as described, including removing the. denickeliz ed; orebetween mixings. The operation is. repeated as many times as necessary.until the required nickel content of the. bath has been reached, afterwhich the metal bath is, removed partially or totally.

Owing to the low nickel content of the ore, a considerable number. ofpourings or other forms of violent intermixings are required in order tosecure, from pure iron, a ferroI-alloy havinga high. enough nickelcontent to make t uitable. for steel making purposes. These repeatedpourings. cool the metal, and in order to overcome this, the ore may beheated to a temperature not only sufficient to melt it but to providesufficient heat tocompensate for the heat lost during the repeatedpourings. Similarlythe ferrous metal bath canbe heated to anfexces stemperature in order to compensate for heat lossesduring thepouringoperationsor both the metal bath and the, ore can be heated to providethe excess heat required in order to, carry out the operation. Anotherway of pr'oyidingaddi; tel. he 2 diamante o he t es d ring. h s: P d. rn sj s o dd. tron o ermic e uci g. agent oi m't ib h The ore can bemelted forinstauce in areuerberatory A e furnace, in a rotating furnace,or in an electric furnace, but in any event, it must be brought to atemperature to make it fluid.

The successive intermixings of molten metal and molten ore can be madeby violently pouring the molten metal into a bath of molten orecontained in a ladle or other receiver. It can be made by simultaneouslypouring both the molten metal and the molten ore into the same receiver.In either case, if the respective amounts of ore and metal have beenproperly chosen, as above indicated, there is a dispersion of the metalinto substantially all of the ore which causes the two materials toapproach substantial equilibrium by the end of the pouring operation.

In one embodiment of the invention, a steel bath containing no nickel oronly a small amount of nickel is violently intermixed with molten lowgrade nickel ore. The denickelized ore is removed from the metal bathand the bath is treated repeatedly with successive charges of fresh lowgrade nickel ore, each treatment involving a violent intermixing of thetwo materials. In carrying out these repeated intermixings of molten oreand molten metal, there may be added to the molten metal prior to eachintermixing or prior to at least some of the intermixings, an exothermicreducing agent which may be silicon, aluminum or carbon or alloys,thereof, in amount sufiicient to maintain the bath at the desiredtemperature during the various intermixings. At. each intermixing,nickel oxide of the ore is reduced to nickel, which enters th bath,thereby enriching it. After the content of nickel in the ferrous metalbath has reached the desired point, the bath is allowed to solidify orelse it is used in the liquid state, as for example by adding it to asuitable steel bath for making 18-8 stainless steel.

In another embodiment of the process, I may start with an iron-nickelalloy already containing a large nickel con tent, for instance of theorder of 35%. This molten alloy is first violently intermixed withmolten low grade nickel ore. During this first intermixing, the nickeloxide of the ore is reduced to nickel and enters the alloy bath, therebyenriching it slightly. The exhausted nickel ore is then removed from thealloy bath. The intermixingoperation is repeated again, using the samealloy bathwith a further charge of molten nickel ore. A weight of alloybath correspondingsubstantially to the surplus metal introduced into thebath from the ore is drawn off from the bath, thus obtaining a highgrade nickel alloy. The previous operation is repeated with theremainder of the alloy bath, intermix-ing it with a new charge of moltenore and; drawing off the exhausted ore, and this cycle, including thedrawing oif of a portion ofthe alloy bath, is repeated in definitely.However, one must take care not to let the nickel content of the alloyrise to too high a value, say over 60% nickel, since, ifthis occurs, thereduction of the nickel oxide in the ore by the alloy bath, will notre.- sult in adequate exhaustion of the ore. In order to prevent thenickel content of the bath from reaching too higha value, iron isintroduced into the bath. Iron can be introduced into the bath in eitherone of the following two waysor by a combination of both. According toone way, a direct addition of iron is made to the bath, Another way isto utilize an ore containing iron oxide,

or by adding iron oxide to a nickel oxide ore. A r ducing agent, forexample siliconor aluminum. or their alloys, is added to the metal bath.During intermixing. of the molten oreand molten metal, the reducing.agent reduces ironoxidein the ore toiron, which enters thefmetal. bath.The reducing agent is employed in such amount. as. to reduce atleastsome of thei onoxideof the ore. In. this manner, iron resulting fromreduction of iron-oxide in the ore enter the bath andprevents thenickel; content ofthe bath; fro reaching toohigh a value, One; may,particularly,

. tiz l i 11 h. n maun Qfi e ucing. al l l h h he p ndmi kc i ish-w leeduce fr m; heqrc, r n h ame-1 t h on. ndmicit l.

in the metallic bath. Under these conditions, the metallic bath does notchange its composition as the successivev intermixings are carried out,but its weight increases each time.

In the case where iron or iron oxide in solid form is added to themetalbath, extra heat must be supplied in order to heat and melt theseintroduced elements. This extra heating may be accomplished by suitablereheating of the-metal bath and/ or the ore, and/or by an appropriateaddition of the reducing agent. The reducing agent in this case must beof such character and used in such amount that the heat liberated by itsreaction with the oxides will be great enough to heat and melt the metalor oxide added and to compensate for the heat losses occurring duringthe operation of the process. Ferro-silicon is particularly suitable foruse as a reducing agent because it is not only a strong reducing agentbut also provides iron.

-The intermixing of the molten ferrous metal and the molten nickel orecan be accomplished by a pouring operation involving the use of a ladle,or it can be accomplished by the use of a rotating or oscillatingfurnace. If a rotating or oscillating furnace is employed, a ferrousmetal bath maybe obtained by reducing slag rich in iron oxide and nickeloxide with a strong reducing agent such as silicon or silico-aluminum.After the slag has been drawn off, a low grade nickel ore in moltenstate is added to the ferrous metal bath and the mixture isviolently'intermixed by rotating or oscillating the furnace in such amanner as to produce a penetration of the metal into the slag.Thereafter, the exhausted ore is removed from the furnace, and theferrous metal bath is treated again with a further quantity of low gradenickel ore. These steps are repeated indefinitely until the desiredamount of ferro-nickel has been withdrawn from the furnace. Thus it ispossible to carry out all of the operations with only one furnace. andcontinued without the need for any electric power, this beingparticularly useful where electric power is expensive or unavailable.

. It will be noted that in one embodiment of the process, the startingmetallic bath is substantially pure iron, whereas in another embodiment,the metallic bath used at the start of the operation contains a largenickel content. These two procedures can be combined. Thus, forinstance, one can start with a metallic bath of substantially pure iron,enrich it in nickel content by successive intermixings with furtherquantities of nickel ore and withdrawal of the exhausted ore until abath containing, say, 40% nickel is obtained. Thereafter, one-half ofthe metal bath is withdrawn, an amount of pure iron equal in weight tothat withdrawn from the bath is added to the remaining portion of thebath, thereby giving a bath containing 20% of nickel. This bath is thenenriched by treating it with successive charges of molten low gradenickel ore and removing the exhausted ore after each treatment until thebath contains a nickel content of 40%. These steps may be repeatedindefinitely.

The following examples further illustrate my process.

Example I The ore treated was a New Caledonian ore containing:

. 1 Percent NiO 5 Fe() 25 Slog 40 MgO Balance One ton of the molten orewas poured intoa ladle and then two tons of molten ferro-nickelcontaining 35% The process can be started.

nickel were violently poured into the molten ore in the ladle. Thereaction between ore and metal was almost instantaneous and waspractically complete; the MO content of the ore fell to 0.20%. Theresulting iron-nickel ing is short.

6 alloy amounted to about two tons and contained 36.5% nickeL,

The exhausted molten ore was removed from the ironnickel alloy bath andthen 25 kgs. of ferro-silicon containing' silicon were added to themetal bath. This slightly lowered the nickel content of the bath. Thebath was then intermixed with a new one ton charge of the ore. The bathof iron-nickel alloythen amounted to 2,075 kgs. and contained about36.8% nickel. 75 kgs. of this alloy were withdrawn from the bath and theoperation was repeated on the remaining metal with an addition offerro-silicon. This resulted in a little more than two'tons of metal.The surplus metal was removed and the operation was carried on for afurther period. After about 10 operations, ten tons of ore had beendenickelizedin this manner and about 700 kgs. of a 37% nickel alloy hadbeen drawn ofi.

Example 2 In this example, a Cuban ore containing a very low content ofnickel oxide was used. The ore contained:

Two tons of the molten ore were poured into a ladle and then two tons ofa 25% Ni ferro-nickel to whichhad been added 25. kgs. of a 75% Siferro-silicon were violently poured into the ore in the ladle. The NiOcontent of the ore dropped to 0.15% and about 2,070 kgs. of an alloycontaining about 25 nickel were obtained.

The denickelized ore was withdrawn from the bath and the bath, after afurther like addition of ferro-silicon, was

violently intermixed with a further quantity of the ore. After the twointermixings, the bath amounted to 2,140 kgs. of iron-nickel alloycontaining about 25% nickel. kgs. of the bath were withdrawn and theoperation -.'was resumed with the remaining two tons of metal fortreating a further molten charge of the ore. This operation may becarried on indefinitely.

In accordance with another embodiment of the invention, molten ore andmolten ferrous metal, for example "iron or ferro-nickel, are placed in areceiver and the mixture of the two materials is blown by a current ofgas so as to create a strong intermixing between the ferrous metal andthe ore. In carrying out this blowing operation, a Bessemer convertermay be employed, preferably a bottom blow converter.

The gas employed may be neutral or reducing. Contrary to allexpectations, I have found also that air is equally suitable in spite ofits oxidizing character toward' the metal. Where air is used as the gas,part of the iron of the bath and part of the reducing elements which maybe added to the iron bath are oxidized by the air, but this does notprevent the remaining iron or reducing agents from reducing nickel oxidein the ore to very low values. This is particularly true where theduration of the NOW In practice, a few seconds of violent blowing aresufficient. Where silicate ores are treated, the lining of the converterpreferably is acid.

During blowing with air or other oxidizing gas, a small amount of ironis oxidized, thus providing additional heat and lowering somewhat theiron content of the bath. This additional heat helps to compensate forthe heat losses occurring during the operation. However, it is advisableto introduce into the metallic bath a small amount of a strongexothermic element which is more easily oxidized than iron. This elementmay be, for example, carbon, manganese, silicon or silicon alloy. Theseare oxidized by the action of the air together with the action of theore which is mixed with the metallic bath. In order to protect the acidlining of the blowing apparatus against attack by the bath, particularlywhere silicate arranges.

ores. are. being used, it is advisable to introduce into the metallicbath, before blowing, a small amount of silicon or silicon alloy. Theamount of this reducing agent is proportioned so that, during theblowing operation, silicate, of iron isformed. If manganese has beenadded to the bath, the amount of silicon or silicon alloy should besutlicient also to form manganese silicate. The reactivity of. thesesilicates with acid linings is very slight.

Where intermixing of the metal bath and molten ore is accomplished byblowing a gas through the mixture, the proportion of ore to metal bathcan be considerably increased, as compared to an intermixing performedby a. pouring operation. Thus in intermixing by pouring, it; isdesirable, although not absolutely essential, that the weight of the orebe not substantially greater than the weight of the metal bath. However,where the intermixing is obtained by blowing a gas through the mixture,the weight of the ore can easily amount to 2 or more times the weight ofthe metal. This greatly reduces the number of intermixings, required forexhausting the same amount of ore of. its nickel content. Theproportions of ore and metal will vary somewhat according to thestrength of the blowing and the nature of the apparatus which is used.Other conditions being equal, the stronger the blowing, the greater maybe the amount of ore.

Air blowing makes it possible, once a particular nickel content has beenobtained in the alloy, to further increase this nickel content byblowing the alloy with air,

but thistime not employing any ore. In this way, a substantialproportion of iron may be oxidized and passes into the slag formedduring the operation without prohibitive concomitant nickel losses.

The following is an example of an embodiment of the invention in which abath of molten ore and ferrous metal are blown with air.

Example 3 The ore treated was a low nickel Cuban ore containing:

Per cent NiO u 1.5

FeO 35 MgQ Balance Two tons of: the molten ore and one ton of molteniron were loaded into a bottom blow acid lined converter. while theconverter was on its side. 7 kgs'. of ferrorsilicon containing 75%silicon were added tothe mixture in the converter, the converter wasraised, and about,- cubic meters of air were blown in 10 seconds. Theconverter was lowered, and the metal was allowed to separate-from themolten ore. The molten ore, after separatiom from the metal, contained0.17% NiO. Theremaining-metal contained about 2% nickel.

7' kgs. offerrosilicon containing 75% silicon were added: to the metalinthe converter and the metal was used. to treat a new two ton charge ofore in the manner described. These operations were repeated many times.After operations, the metal bath weighed 9-50 kgs. and contained about30% of nickel.

In another embodiment of the invention, the molten iron or moltenferro-nickel contains a small amount of carbon, and the inter-mixing ofthe metal with the molten ore is obtained by pouring the molten metalinto'the molten ore, or by the simultaneous pouring of both the moltenmetal and the molten ore into a ladle or other receiver. The action ofthe carbon on the ore creates a strongbubblingwhichaidsin mixing the twomaterials. The carbon reacts with the iron-and nickel oxides containedin the molten ore, liberating carbon monoxide which causes bubbling ofthe mixture. The pouring must not be so violent asto cause= the mixtureto over flow from the ladle. If the pouring is made rather slowly; thecarbon monoxide-released causes rather strong bubthe mixture.

accomplished by pouring without bubbling.

The amount of carbon introduced or contained inthemetal bath may besmall, say 0.2 to 0.5%. Some carbon can. be added between successiveintermixings, if the bath becomes too poor in carbon so that bubblingnolonger is. strong enough.

Other reducing elements can also be added, such as aluminumv or siliconor their alloys, in order to increase the exothermicity of the reducingreaction. However, the bubbling may be decreased or delayed due to thestronger reducing action of the aluminum or silicon on the nickel andiron oxide in the ore.

The metal bath which is used for treating successive charges of moltenore may be either iron containing carbon or ferro-n-ickel' containingcarbon. The latter can be obtained by reduction, of nickel ore or slagwith carbon or by any other means. I

The: following is an example of this embodiment of the: invention.

Example 4 The ore, treated contained:

Per cent Nio 5.7 FeO 25 SiOz 40 Mg Balance Two. tons of this molten orewere tapped into'a ladle. Carbon inthe. amount of 0.3% and silicon inthe amount of 0.15%. were added to a two ton bath of' ferro-nickelcontaining 32% nickel, and this bath was then cautiously poured into themolten ore in the ladle. The pouring lasted'about 5 minutes: and causeda strong bubbling of The ore and the metal were allowed to separate andthe exhausted ore was removed from the metal. The orecontained' only0.15% NiO. The metal contained.36.30% nickel. The silicon and carbonwere practically wholly oxidized.

These operations were repeated many times, using the same metal bath andtwoton charges of new ore, and" adding to the metal bath before eachpouring 0.2% car bon and 0.15% silicon. After five pourings, ten tonsofore had been exhausted of its nickel content; weight of the metal hadincreased slightly, and' its nickel content was 52%.

The discontinuous processes above described secure excellent exhaustionof the ore, but they require manyhandlings of the ore and metal,particularly where the nickel. content ofthe ore' is low and manyintermixings are required to provide ferro-nickel of desired nickelcontent. A continuousprocess will now be described in which theoperations-can be efiectively carried out with a minimum of labor andmaintenance of the equipment employed.

CONTINUOUS PROCESS Refer-ringmore particularly to the accompanyingdrawings and. for the present to Figures 1 and 2, there is provided anelongated cylindrical vessel 2 lined with refractory material and openat each end. The vessel extends.

introduced into the vessel prior to the introduction of" The the moltenore through the chute 4. During the passage of the molten ore throughthe vessel 2, the latter is rotated so as to secure intimate mixing ofthe molten ore and molten metal bath. The vessel is provided with tiresor wheels 9 which rest on rollers 10. The vessel also is provided with agear wheel 11 which is driven by any suitable means (not shown) in orderto rotate the vessel.

An externally water-cooled tube 12 extends through an.

opening 13 in the end of the vessel opposite the molten ore supply chute4 for supplying reducing agent, as for example silicon, ferro-silicon oraluminum to the molten ore in the vessel. The reducing agent is fed intoa hopper 14 communicating with the tube 12 and is conveyed by a screw(not shown) located in the tube to the inner end of the tube where itfalls through openings 15 onto the molten ore in the vessel. Aninternally water-cooled tube 16 also extends into the vessel through theopening 13 and carries a bafile 17 which dips into the molten ore 18which is on top of the molten metal bath 19 and prevents the reducingagent from flowing out of the vessel. The opening 13 is closed by arefractory piece 20. Ferro-nickel produced in the reduction process iswithdrawn from the vessel 2 through a tap hole 21. By way of example butnot limitation, the rotatable vessel 2 may have a length of about 7 /2meters and an internal diameter of 2 /2 meters.

In the embodiment illustrated in Figures 3-5, parts corresponding tothose shown in Figures 1 and 2 are designated by the same referencenumerals with the letter a sufiixed. This embodiment is similar to thatshown in Figures 1 and 2 except that the vessel 2a, instead of beingcylindrical throughout its length, has a non-cylindrical cross-sectionat the portion 25 which is adjacent the end of the vessel through whichthe molten ore is supplied. The remaining portion 26 of the vessel iscylindrical in cross-section. The non-cylindrical section 25 providesmore effective intermixing of the molten ore and molten metal than doesthe cylindrical section 26.- Thus in this embodiment, the molten ore andmolten metal are vigorously intermixed while in the portion 25, afterwhich the molten ore and molten metal flow into the portion 26 Where nomore intermixing occurs and there is an opportunity for metal globulesin the molten ore to settle from the ore into the metal bath 19a.

By way of example but not limitation, the cylindrical portion 26 of thevessel 2a may have a length of 3%. meters and the non-cylindricalportion 25 a length of 4 /2 meters. The major axis X of thenon-cylindrical portion 25 may be 2.7 meters long, and the minor axis Y2.2 meters long.

- In the embodiment illustrated in Figures 6 and 7, parts correspondingto thoseshown in Figures 1 and 2 are desig, nated by the-same referencenumerals with the letter b sufiixed. Inthis embodiment, the rotatablevessel 2b is cylindrical throughout its working portion, but is providedin the portion 28 adjacent the charging opening b with longitudinallyextendinginwardly projecting ribs 29. The remaining portion 30 iscylindrical. Thus, as in the'embodiment shown in Figures 3-5, vigorousintermixing of the molten ore and molten metal is obtained while the oreis in the portion 28, but when the ore passes into the portion 30, anymetal globules entrapped in the molten ore have an opportunity to settleinto and be incorporated into the molten metal bath. 7

Due to the increased intermixing obtained in the portions 25 and 28 ofthe rotatable vessels shown in Figures 3-7, as compared with theembodiment shown in Figures 1 and 2, a larger quantity of ore can betreated in a given size vessel or the size of the vessel can be reducedwhile treating the same quantity of ore where increased agitation isprovided.

The apparatus described above does notinclude heating means, whichconsiderably simplifies its structure. Such heat as is required tomaintain the molten charge within the apparatus at the desiredtemperature. may be supplied by the addition of reducing agents (such asferrosilicon or aluminum) which react exothermically with iron oxide andnickel oxide present in the ore.

As the apparatus rotates, its interior wall surface is wetted by a layerof the molten ore, and this layer solidifies as it is carried upwardlyand out of contact with the molten ore charge. Such solidified layerforms a constantly renewed protective lining for the apparatus. Whencontinued rotation of the apparatus carries" the solidified layer againbeneath the surface of the molten charge, it remelts, but at leastpartially it does so only after being carried to beneath the surface ofthe molten metal layer. Thereby globules of ore are released below themetal surface and rise upwardly through the metal, with the result thatthe intimacy and extent of reactive contact between molten ore andmolten ferrous metal are increased.

The quantity of ore present at all times in the appa ratus must not betoo high compared with the quantityof ferrous'xnetal present at the sametime, otherwise it is not possible to obtain an effective intermixing ofboth phases and consequently a complete exhaustion of the nickel fromthe ore. However, the stronger the intermixing and the longer thepassage of the ore through the apparatus, the more the amount of orepresent at any time can be increased. But the quantity of metal willalways have to be much greater than the quantity of nickel contained inthe ore present in the apparatus at a given time. Thus, for instance, ifthe vessel contained one ton of molten ore containing 3% NiO and theiron in the metal bath amounted to only about 25 kgs., it would bepractically impossible to secure substantially complete exhaustion ofthe nickel content of the ore in its passage through thevessel.

Several variants are possible in carrying out the continuous processirrespective of the particular form of rotatable vessel which isemployed. These variants correspond substantially to those described inconnection with the discontinuous processes. As a first variant, one maystart with a molten charge of pure iron or iron containing a low nickelcontent, and gradually build up the nickel content of the, metal bath bysubstantially continuously passing molten ore through the rotatingvessel in contact with the metal bath. When the ferro-nickel hasacquired the desired nickel content, it may be removed .from the vesseland a new charge of pure iron. or ironcontaining a low nickel contentmay be placed in the vessel and the process repeated.

As a second variant, the vessel may be charged with a ferro-nickelhaving the desired nickel content and molten ore may then be flowed overit continuously while rotating the vessel and supplying reducing agent,for example, ferro-silicon, which is capable of reducing iron oxide andnickel oxide contained in the ore. Preferably the reducing agent is usedin an amount so proportioned that the'quantity of metallic ironintroduced into the molten ferro-nickel by reaction of the reducingagent with the iron oxide of the ore is in substantially thesameproportion to the amount of metallic nickel introduced into the moltenferro-nickel by reduction of the nickel oxide of the ore as is theproportion of iron to nickel in the ferro-nickel. Thus, the nickelcontent of the ferronickel remains substantially constant throughout theprocess but its Weight increases. Ferro-nickel is withdrawn from thevessel from time to time or continuously.

Of course, any combination of the two above described variants may beemployed.

In carrying out the invention, the rate at which the molten ore isdelivered to the surface of the metal bath in the rotatable vessel islimited to the rate at which the nickel content of the ore can besubstantially completely reduced and can be incorporated in the metalbath in a single passage through the vessel. One can use in theapparatus all known methods for increasing the intermixing between oreand metal, for example blowing of 11 gas, production of CO by additionof carbon: to the metallic bath, .etc.

The; following examples illustrate various. ways in which the processcan be carried outrin a continuous manner.

Example The orewhich was treated had the following composition:

In carrying out this example, the apparatus shown in Figures 1 and 2 wasemployed. Ten tons of molten steel were charged into the vessel 2', andthen molten ore previously melted in a separate reverberatory furnacewas. introduced into the vessel 2 throughv the chute 4 until the orereached approximately the level of the dam 7. The vessel was revolved ata speed of 4 revolutions per: minute and after a short time, freshmolten orewas poured into the vessel through the chute 4- substantiallycontinuously at a rate of 20 tons per hour while the vessel'wasrotating. Every ten minutes, 815 kgs. of'ferrosilicon containing 75%silicon were introduced into the vessel through the tube 12. The addedferro-silicon melted and dissolved in the metal bath 1-9. The molten oreflowed through the furnace and over the dam 7 and into the chute S. Theore was substantially completely exhausted of its nickel content in asingle passage through the vessel, its NiO content at the exit end ofthe vessel being of the order of 0.15%. After the process had beencontinued for 8 hours, the metal bath had become a ferro-nickelcontaining 50.3% nickel. The operation was stopped, the ferro-nickelwithdrawn through the tap hole 21, a new charge of molten steel wasintroduced into the vessel, and a new operation was begun;

Example 6 The ore treated had the following composition:

Percent- NiO 1.89 FeO 13.50 SiO2 46 MgQ+AlzO3 Balance while 25 kgs. offerro-silicon containing. 75% silicon. The;

were introduced. into the vessel every 5 minutes. depleted molten oredischarged over the dam 7a contained 0.10% NiO. After working for aperiodof about 12 hours, the operation was stopped. The metallic bathhad approximately doubled in weight and contained about 50.3% nickel. Itis seen that in carrying out this step of the process, the ferro-siliconwas used'in such amount that the iron and nickel reduced from the orewere in approximately the same proportions as the iron and nickel in theferro-nickel bath so that the composition ofthe ferro-nickel bathremained substantially constant, but its weight increased. Ten tons ofthe f'erro-nickel were then removed from the vessel and anotheroperation was begun using the tons of ferro-nickel remaining-in thevessel'and-repeating' the operationas described.

12 Example 7 i The same ore as given in Example 1 was treated but thetreatment was carried out in apparatus of the type shown in Figures3-5'.

Ten tons of molten'ore were poured into the. vessel 2a, and the vesselwas rotated. During the first half-hour, 800 kgs. of ferro-siliconcontaining 75 silicon were introduced. At the end of this firsthalf-hour period, there had been produced. 2300 kgs. of a metallic bathcontaining 14% nickel, the rest being mainly iron.

The vessel was then charged with fresh molten ore. up to a level ofabout 20 centimeters below the top of the dam 7a. while the vessel wasrotating and then while the vessel continued to rotate, molten ore wasintroduced. continuously together with kgs. of ferro-silicon (75 Si) perton of ore. After the molten ore had reached the top of the darn, itoverflowed from the vessel. During a period of 1 /2 hours, 35 tons ofmolten ore were treated so as to substantially completely exhaust theore of its nickel content. In this period, the bath increased in weightto about 10 tons but its nickel content remained substantially at 14%becausethe proportion of iron and nickel reduced from the ore wasapproximately the same as that in the metal bath.

After the weight of the metallic bath had reached about 10 tons, theamount of ferro-silicon introduced into the vessel was decreased to 3kgs. per ton of ore while the ore was passed through the rotating vesselat the rate of 30 tons per hour. The bath grew progressively richer innickel, without greatly changing its weight, so that after 4 hours, itsnickel content had been increased to about 50%.

The operation was then continued by supplying ore, to.

the vessel at the rate'of 30 tons per hour, but the amount offerro-silicon containing 75% silicon was increased to 22 kgs. per ton ofore. After this step had been continued for 5 /2 hours, the weight of.the bath had increased to about 20 tons but its nickel. content remainedat about 50% because during this step, both iron and nickel were reducedfrom the ore, and in approximately the proportions of these elements inthe metal bath.

Rotation of' the vessel was then stopped, and ten tons of the metal werewithdrawn. The operation was then resumed using the 10 tons of metalremaining in the vessel and employing the same working conditions, i.e., a. flow of 30 tons. of ore per hour through the vessel while adding22 kgs. of ferro-silicon perton of ore. This operation' was continueduntil the metal bath weighed about 20 tons, after which half of it waswithdrawn and the process continued in a like manner.

The invention is not limited to the preferred embodiments, but may beotherwise embodied or practiced'within the scope of the followingclaims.

I claim:

1. A process for extracting nickel from low grade nickel ores containingan' oxidic compound of nickel, which comprises violently intermixingmolten low' grade nickel ore with a bath of ferro-nickel containing atleast 25 by weight of nickel to reduce nickel oxide from the ore andintroduce'it into the metal of the bath, removing the denickelized orefrom the bath, also withdrawing a portion of the ferro-nickel from thebath, adding a reducing agent to the remainder of" the metal bath, then.

intermixing the remainder of the metal bath with a further quantity ofmolten low grade nickel ore, and repeating' the above described sequenceof operations;

2. A process for extracting nickel from a' low grade nickel orecontaining iron and nickel in the form of oxidic compounds, whichcomprises forming a molten bathv of said ore, vigorously intermixingwithsaid molten bath a quantity of molten ferro-nickel containing areducing.

agent for ferrous oxide and nickel oxide, the amount of reducing agentbeing such as to reduce iron: and nickel from the ore'in' about the sameproportionasthe propor- 13 tion of iron to nickel in the ferro nickel,whereby'the weight of ferro-nickel is increased while maintaining itspercentage content of nickel substantially undiminished, withdrawing aportion of the ferro-nickel, and utilizing the remainder of theferro-nickel for the treatment of a further quantity of molten ore.

3. A process for extracting nickel from low grade nickel ores containingoxidic compounds of nickel and iron, which comprises violentlyintermixing the molten ore with molten ferro-nickel containing at least25% by weight of nickel and also containing a reducing agent for ironoxide, said reducing agent being in amount sufficient to reduce ironoxide in the ore and introduce it into the ferro-nickel bath, wherebythe concentration of nickel in the metal bath is limited, and repeatedlyintermixing the ferro-nickel bath with successive charges of said moltenore, said ferro-nickel bath having quantities of said reducing agentadded to it prior to at least some of the successive intermixings.

4. A process for extracting nickel from low grade nickel ores containingan oxidic compound of nickel, which comprises intermixing ferro-nickelcontaining carbon and at least 25% by weight of nickel and a bath ofmolten low grade nickel ore containing oxidic compounds of nickel andiron by a pouring operation, whereby vigorous evolution of carbonmonoxide ensues and effects thorough intermixing of the moltenferrO-nickel with the molten ore, and whereby the nickel content of theore is substantially completely reduced to metallic nickel and isincorporated in the ferro-nickel bath, removing the denickelized orefrom the ferro-nickel bath, and repeatedly adding carbon to theferro-nickel bath and intermixing it with successive charges of themolten low grade nickel ore.

5. A process for recovering nickel from a low grade ore containingnickel in the form of an oxidic compound which comprises continuouslyflowing such ore in the molten condition over the surface of a bath ofmolten ferrous metal, subjecting the molten ore and the molten metalbath to an intermixing action, maintaining the molten ore in contactwith the molten bath for a sulficient period of time for the nickel ofthe ore to be substantially completely reduced by the iron of the bathand to become incorporated in the bath, substantially continuouslywithdrawing the molten ore residue after it has become substantiallycompletely depleted of nickel, and withdrawing molten ferrous metalcontaining nickel in a substantially higher concentration than the orefrom said bath.

6. A process for recovering nickel from a low grade nickel orecontaining oxidic compounds of iron and nickel which comprisescontinuously flowing such ore in the molten condition over the surfaceof a bath of molten ferro-nickel, subjecting the molten ore and themolten metal while in contact with each other to a stirring action,treating the molten ore while in contact with the molten ferro-nickelwith a reducing agent for iron oxide in an amount so proportioned to thenickel content of the ore that the quantity of metallic iron introducedinto the molten ferro-nickel by reaction of said reducing agent with theiron oxide of the ore is in substantially the same proportion to theamount of metallic nickel introduced into the molten ferro-nickel byreduction of the nickel oxide of the ore as is the proportion of iron tonickel in the ferro-nickel, maintaining the molten ore in contact withthe molten ferro-nickel until the ore has been substantially completelydepleted of nickel, substantially continuously withdrawing the depletedore residue, and withdrawing molten ferro-nickel from said bath at sucha rate as to maintain the total volume of said bath approximatelyconstant.

7. A process for recovering nickel from a low grade ore containingnickel in the form of an oxidic compound which comprises introducing abath of molten metallic iron into a rotary vessel, melting said ore anddelivering a substantially continuous flow of the molten ore on to thesurface of said bath, promoting an intermixing between the molten ironand the molten ore by substantially continuously rotating said vesselabout a substantially horizontal axis, maintaining the molten ore incontact with the molten metallic bath until the nickel content of theore has been substantially completely reduced by reaction with themolten iron, substantially continuously withdrawing molten ore residuedepleted of nickel from said vessel, and withdrawing metal from saidbath when the nickel content thereof has been built up sufliciently toform a ferro-nickel of desired grade.

8. A process for recovering nickel from a low grade ore containingnickel in the form of an oxidic compound which comprises introducing abath of molten metallic ferro-nickel into a rotary vessel, melting saidore and delivering a substantially continuous flow thereof on to thesurface of said bath, stirring the molten ore into effective reactivecontact with the iron of said bath by substantially continuouslyrotating said vessel about a substantially horizontal axis, maintainingthe molten ore in contact with the molten metallic ferro-nickel for asufiicient period of time for the nickel content of the ore to besubstantially completely reduced by reaction with the iron of theferro-nickel and'to become incorporated in the ferro-nickel,incorporating fresh metallic iron in the ferronickel in the sameproportion to the amount of nickel incorporated therein by reductionfrom the ore as the initial proportion of iron to nickel in theferro-nickel, whereby the composition of the ferro-nickel is maintainedsubstantially constant, substantially continuously withdrawing moltenore residue depleted of nickel from over said bath, and withdrawingferro-nickel from said bath as required to maintain'the volume thereofin the vessel approximately constant.

9. A process for recovering nickel from a low grade ore containingnickel in the form of an oxidic compound which comprises introducing amolten metallic bath comprising iron into a rotary vessel, melting saidore and substantially continuously delivering a flow of the molten oreon to the surface of said bath, stirring the molten metallic bath andthe molten ore into effective reactive contact by substantiallycontinuously rotating said vessel about a horizontal axis, limiting therate at which molten ore is delivered to the surface of the bath to therate at which the nickel content of the ore can be substantiallycompletely reduced by reaction with the iron of the bath and can beincorporated in the bath, substantially continuously withdrawing thespent ore melt after it has been substantially completely depleted ofnickel from the surface of said bath at a point remote from where it isdelivered on to the bath and at substantially the same rate as it isdelivered thereto, and recovering the nickel reduced from the ore in theform of metallic ferro-nickel withdrawn from said bath.

10. A process for recovering nickel from a low grade nickel orecontaining oxidic compounds of iron and nickel which comprisesintroducing a bath of molten metallic ferro-nickel into a rotary vessel,melting said ore and substantially continuously delivering a flow of themolten ore on to the surface of said bath, stirring the molten ore intoetfective reactive contact with the ferro-nickel by substantiallycontinuously rotating said vessel about a substantially horizontal axis,limiting the rate at which molten ore is delivered to the surface of thebath to the rate at which the nickel content of the ore can besubstantially completely reduced by reaction with the metallic bath andcan be incorporated in the bath, adding to the bath while in contactwith the molten ore a reducing agent for iron oxide in an amount soproportioned to the nickel content of the ore that the quantity ofmetallic iron introduced into the molten ferronickel by reaction of saidreducing agent with the iron oxide of the ore is in substantially thesame proportion to the amount of metallic nickel introduced into themolten ferro-nickel by reduction of the nickel oxide of 15 the. ore asis the proportion of iron to nickel in the ferronickel, substantiallycontinuously withdrawing the ore melt after it has been substantiallycompletely depleted of nickel from the surface of the bath offerro-nickel at' a point remote from where it is delivered on to thebath and at substantiallythe sarnerate as it is delivered thereto, andrecovering the nickel and iron reduced from the ore in the form offerro-nickel by withdrawal thereof from said bath.

11. In a processfor the recovery of nickel from a low grade orecontaining nickel in the form of an oxidic compound, the steps whichcomprise substantially continuously delivering a molten stream of theore to the surface of a molten metallic bath comprising iron andsubstantially continuously withdrawing the ore melt depleted in nickelfrom the surface of said metallic bath, subjectiug the molten ore andthe molten metallic bath to an intermixing action at' a region remotefrom the point of withdrawal of the depleted ore melt, thereby to insureeiiective reactive contact between the molten ore and the moltenmetallic bath, and maintaining the molten ore and molten metallic bathrelatively quiescent in the region adjacent the point of withdrawal ofthe depleted ore melt, thereby to enable substantially unhinderedsettling of metallic particles from the ore. melt immediately prior toWithdrawal of said melt.

12. A process for recovering nickel from a low grade ore containingnickel in the form of an oXidic compound, which comprises introducing amolten metallic bath comprising iron into a rotary vessel, melting saidore and substantially continuously delivering a flow of the molten oreon. to the surface of. said bath, flowing the molten ore in contact withthe surface of said bath successively through a first zone and thenthrough a second zone, limiting the rate at which molten ore isdelivered to the surface of the bath to the rate at which the nickelcontent of the ore can be: substantially completely reduced by reactionwith the iron of the bath and can be in-,

corporated in the bath in passing through said zones, stirring themolten metallic bath and the molten ore into effective reactive contactwhile in the first zone by substantially continuously rotating saidvessel, decreasing the amount of stirring of the molten ore during its,passage through the second zone to cause eifective settling of metalglobules from the ore into the metallic bath, substantially continuouslywithdrawing the spent ore melt afterit has been substantially completelydepleted of nickel from the surface of said bath after it has passedthrough the second Zone, and recovering the nickel reduced from the orein the form of metallic ferro-nickel withdrawn from said bath.

References Cited in the file of this patent UNITED STATES PATENTS476,913 Wood June 14, 1892 1,300,279 Kissock Apr. 15, 1919 1,415,183Lund May 9, 1922 1,421,185 Driscoll June 27, 1922 1,546,965 BlessingJuly 21, 1925 1,647,381 Tharaldsen Nov. 1, 1927 1,938,832 Hougen et al.Dec. 12, 1933' 2,100,265 Perrin Nov. 23, 1937 2,622,977 Kalling et al.Dec. 23, 1952

1. A PROCESS FOR EXTRACTING NICKEL FROM LOW GRADE NICKEL ORES CONTAINING AN OXIDIC COMPOUND OF NICKEL, WHICH COMPRISES VIOLENTLY INTERMIXING MOLTEN LOW GRADE NICKEL ORE WITH A BATH OF FERRO-NICKEL CONTAINING AT LEAST 25% BY WEIGHT OF NICKEL TO REDUCE NICKEL OXIDE FROM THE ORE AND INTRODUCE IT INTO THE METAL OF THE BATH, REMOVING THE DENICKELIZED ORE FROM THE BATH, ALSO WITHDRAWING 